It is sometimes necessary to introduce pharmacologically active substances into body cavities, such as the urethra or the rectum of a patient. One instance of this is the introduction of a local anesthetic into the urethra prior to the insertion of a catheter or similar into the urethra in order to alleviate the discomfort and pain experienced by the patient during this operation. The local anesthetic may for instance be introduced through a tubular part inserted into the body cavity in question.
In order that the patient may not experience the same discomfort during the introduction of the anesthetic as during the actual insertion of the catheter, very high demands have to be made on the shape and smoothness of the tubular part and particularly on the tip thereof.
These demands easily can be met if a reusable, tubular part made of a permanent material without an integral seal is used in accordance with the long-established prior art. However, such a tubular part normally would have to be sterilized before a renewed use which is one reason why they no longer are much in use.
Instead prefilled, disposable devices are nowadays used extensively in hospitals, medical practices etc. These devices are normally delivered in a sterile condition in the form of sealed containers normally having a frangible seal in or on a dispensing outlet. In a device of the kind mentioned above in the introduction, the dispensing outlet of course would be the opening in the tubular part. When designing the frangible seal, the fact that this opening may not have any sharp edges after removal of the frangible seal must be taken into consideration, since such sharp edges would cause the patient pain or other discomfort when the tubular part is inserted into the body cavity.
One solution to this problem is disclosed in AT-B-386 123. This document discloses a device for introducing a lubricating substance into the urethra in order to facilitate a subsequent insertion of a catheter. The device comprises two parts, namely a bellow-shaped container and a funnel-shaped part ending in a tubular part. The free end of the tubular part is sealed by means of a frangible seal. The container and the funnel-shaped part are ultrasonically welded together. The opening at the free end of the tubular part has rounded edges and the frangible seal is located a slight distance within the tubular part. The frangible seal is provided with an integrally formed actuating rod projecting outside the opening and the frangible seal is broken upon actuation of the rod.
CH-A-608 373 discloses another device of the same general kind as the prior art device described above, the main difference being the field of application, which in this case is the introduction of a pharmacologically active substance into the rectum of a patient.
There are however some factors that have to be considered when designing and manufacturing a device of the kind described above. When such a device is opened, the frangible seal always should be ruptured in a clearly defined way without leaving any projecting parts or loose splinters which may inconvenience or harm the patient. This means that a very high standard must be met in regard of the homogenity of the material in the actuating rod, in the frangible seal and in the tubular part as well as in regard of the accuracy in size of these parts.
The frangible seal also should be ruptured in said clearly defined way irrespective of the manner in which the actuating rod is operated.
Depending on the kind of body cavity into which the tubular part is to be inserted, a high standard may have to be set regarding the sterility of the tubular part, particularly if the cavity in question is the urethra.